The amino acid sequence of a new pancreatic polypeptide hormone (APP) from chickens has been completed. It is Gly.Pro.Ser.Gln.Pro.Thr.Tyr.Pro.Gly.Asp.Asp.Ala. Pro.Val.Glu.Asp.Leu. Ile.Arg.Phe.Tyr.Asp.Asn.Leu. Gln.Gln.Tyr.Leu.Asn.Val.Val.Thr.Arg.His. Arg.Tyr.NH2. This peptide has been localized by immunoassay to pancreas of chickens and has been demonstrated in chicken plasma. APP levels are 2-4 ng/ml in fasted birds and rise to plus or minus 20 ng/ml one hour after feeding is allowed. At midday, in birds fed ad libitum the plasma levels are about 8 ng/ml and in pancreatectomized chickens under the same conditions about 1 ng/ml. Mechanical distention of the crop does not stimulate APP secretion.